docs: def babel_compile(source, **kwargs):
      """Compiles the given ``source`` from ES6 to ES5 using Babeljs"""
      presets = kwargs.get('presets')
      if not presets:
          kwargs['presets'] = ["es2015"]
      with open(BABEL_COMPILER, 'rb') as babel_js:
          return evaljs(
              (babel_js.read().decode('utf-8'),
               'var bres, res;'
               'bres = Babel.transform(dukpy.es6code, dukpy.babel_options);',
               'res = {map: bres.map, code: bres.code};'),
              es6code=source,
              babel_options=kwargs
          )